1. Field of the Invention
This invention relates generally to machinery devices and more particularly to devices for machining the open ends of lengths of pipe.
2. Description of the Prior Art
In the production of pipe, as lengths of pipe are produced it is necessary to finish surface and deburr both ends of each length of pipe. In modern, high-volume production operations this requirement often becomes the pacing item in attempting to achieve higher production rates. The finish surfacing and deburring typically consists of first machining the end surface to be flat, smooth and perpendicular to the longitudinal axis of the pipe, then removing the burrs from the inner and outer edges. It is relatively simple and quick to precisely locate the pipe radially for this finishing operation using V-shaped clamps or similar locating, clamping means. However, precisely locating the pipe end laterally along its axis is much more difficult and time consuming. Moreover, the length of the pipe may vary considerably. As a result, most pipe finishing operations only locate the pipe nominally in the longitudinal direction. Existing double end, tube end finishing machines can not compensate for variations in pipe lengths of 1/16 inch or greater.
The tools typically used for the finish surfacing, deburring and beveling are standard machine tool cutters and grinders. Such tools are subject to fracture under impact shocks and operate most efficiently at a relatively slow drive speed. Consequently, a typical pipe end finishing operation consists of driving the tools under fast feed until they are almost at a position to contact the workpiece, if the workpiece is located at the innermost limit of the positioning tolerance. The drive is then shifted to slow feed until the tools actually contact the workpiece and throughout the machining operation. Of course, if the workpiece is located at the outermost limit of the positioning tolerance, the tools have to traverse the entire width of the positioning tolerance at slow feed which represents a considerable waste of time. A proportionate waste of time occurs for all intermediate longitudinal positions of the workpiece.
Other methods utilize multiple passes requiring more complex and costly machinery and usually requiring comparable time or longer. For example, the end finishing tool may be brought to the end of the pipe in an operation similar to that described above and, after the pipe end is faced, the deburring tools radially displaced to contact the workpiece (see U.S. Pat. Nos. 3,280,672; 3,796,116; and 2,030,562). Alternatively, a turret lathe using a live spindle and multiple tools mounted on a driven turret (see U.S. Pat. No. 4,058,033) may be employed. Although these other methods require complex and costly machine tools, they do not solve the basic problem.